Light emitting diode (led) components including led dies that are directly attached to lead frames, and methods of fabricating same

ABSTRACT

A Light Emitting Diode (LED) component includes a lead frame and an LED that is electrically connected to the lead frame without wire bonds, using a solder layer. The lead frame includes a metal anode pad, a metal cathode pad and a plastic cup. The LED die includes LED die anode and cathode contacts with a solder layer on them. The metal anode pad, metal cathode pad, plastic cup and/or the solder layer are configured to facilitate the direct die attach of the LED die to the lead frame without wire bonds. Related fabrication methods are also described.

BACKGROUND

Various embodiments described herein relate to light emitting devicesand assemblies and methods of fabricating the same, and moreparticularly, to Light Emitting Diodes (LEDs), assemblies thereof andfabrication methods therefor.

LEDs are widely known solid-state lighting elements that are capable ofgenerating light upon application of voltage thereto. LEDs generallyinclude a diode region having first and second opposing faces, andinclude therein an n-type layer, a p-type layer and a p-n junction. Ananode contact ohmically contacts the p-type layer and a cathode contactohmically contacts the n-type layer. The diode region may be epitaxiallyformed on a substrate, such as a sapphire, silicon, silicon carbide,gallium arsenide, gallium nitride, etc., growth substrate, but thecompleted device may not include a substrate. The diode region may befabricated, for example, from silicon carbide, gallium nitride, galliumphosphide, aluminum nitride and/or gallium arsenide-based materialsand/or from organic semiconductor-based materials. Finally, the lightradiated by the LED may be in the visible or ultraviolet (UV) regions,and the LED may incorporate wavelength conversion material such asphosphor.

An LED component provides a packaged LED die for mounting on a board,such as a Metal Core Printed Circuit Board (MCPCB), flexible circuitboard and/or other printed circuit board, along with other electroniccomponents, for example using Surface Mount Technology (SMT). An LEDcomponent generally includes an LED die and other packaging elements.

SMT is a method for producing electronic circuits in which thecomponents are mounted or placed directly onto the surface of circuitboards. An electronic device so made may be called a Surface MountDevice (SMD). An SMT component is usually smaller than its through-holecounterpart. Simpler and faster automated assembly may also be provided,as well as other potential advantages. As such, SMT is increasinglybeing used in electronic component assembly.

SMDs often use lead frames as part of the SMD package. A lead frame is ametal structure inside a package that carries signals from the die tothe outside. The die inside the package is typically glued to the leadframe and bond wires attach the die contacts to the lead frame leadsusing wire bonding techniques. The lead frame may then be molded in aplastic case, and the outside of the lead frame is cut off, therebyseparating the leads. The lead frame itself may be manufactured byremoving material from a flat plate of copper or copper-alloy, byetching, stamping and/or other techniques.

Lead frames are also now being used for low cost, high density SMD LEDcomponents. In these LED components, the lead frame includes a metalanode pad, a metal cathode pad and a plastic cup on the metal anode padand the metal cathode pad that defines an exposed portion of the metalanode pad and an exposed portion of the metal cathode pad in the plasticcup. At least some portions of the plastic cup may be transparent,translucent, opaque and/or reflective, and the plastic cup may be formedof plastics, such as Epoxy Molding Compounds (EMCs) and/or silicone. AnLED die is glued to the lead frame, and the anode and/or cathodecontacts thereof are wire-bonded to the lead frame pads. The cup maythen be filled with encapsulant, at least some portions of which may betransparent, translucent and/or reflective. The encapsulant may includewavelength conversion material, such as phosphor, therein.

LEDs are increasingly being used in lighting/illumination applications,with a goal being to provide a replacement for the ubiquitousincandescent light bulb. The cost of manufacturing LED dies may continueto decrease due to advances in microelectronic fabrication techniques.As such, the packaging the LED dies may assume a larger and larger costof the LED component.

SUMMARY

A Light Emitting Diode (LED) component according to various embodimentsdescribed herein includes a lead frame and an LED die that iselectrically connected to the lead frame without wire bonds. In someembodiments, the lead frame comprises a plastic cup, and the LED die isin the plastic cup and is electrically connected to the lead frame inthe plastic cup. In some embodiments, the LED die anode and cathodecontacts are directly attached to the lead frame using a solder layer.

More specifically, an LED component according to various embodimentsdescribed herein includes a lead frame that comprises a metal anode pad,a metal cathode pad and a plastic cup on the metal anode pad and themetal cathode pad that defines an exposed portion of the metal anode padand an exposed portion of the metal cathode pad in the plastic cup. TheLED component also includes an LED die that comprises first and secondopposing faces and an anode contact and a cathode contact on the firstface thereof, the anode and cathode contacts including outer facesremote from the LED die. The LED die is disposed in the plastic cup suchthat the outer face of the anode contact is closely spaced apart fromthe exposed portion of the metal anode pad and the outer face of thecathode contact is closely spaced apart from the exposed portion of themetal cathode pad. The LED component also includes a die attach layerthat extends between the outer face of the anode contact and the exposedportion of the metal anode pad and between the outer face of the cathodecontact and the exposed portion of the metal cathode pad. The die attachlayer directly electrically connects the outer face of the anode contactto the exposed portion of the metal anode pad and directly electricallyconnects the outer face of the cathode contact to the exposed portion ofthe metal cathode pad.

In some embodiments, the plastic cup comprises silicone and the exposedportions of the anode and cathode pads are not coplanar.

According to some embodiments described herein, the metal anode pad, themetal cathode pad and/or the plastic cup are configured to facilitatethe direct electrical connection of the outer face of the anode contactto the exposed portion of the metal anode pad and the direct electricalconnection of the outer face of the cathode contact to the exposedportion of the metal cathode pad, by the die attach layer. Specifically,in some embodiments, adjacent ends of the metal anode pad and the metalcathode pad define a gap therebetween, wherein the plastic cup extendsin the gap and also extends beyond non-adjacent ends of the metal anodepad and the metal cathode pad by a distance. The distance is larger thanthe gap. In some embodiments, the distance is at least 10% larger thanthe gap. In other embodiments, the distance is at least 30% larger thanthe gap.

Still other embodiments can configure the metal anode pad, the metalcathode pad and/or the plastic cup to facilitate direct electricalconnection of the LED to the lead frame by configuring adjacent ends ofthe metal anode pad and the metal cathode pad to have different widths.In yet other embodiments, the plastic cup extends on opposite faces ofthe metal anode pad and/or the metal cathode pad. In still otherembodiments, the lead frame further comprises a metal link thatmechanically connects the metal anode pad to the metal cathode padoutside the plastic cup. The metal link may be configured to shearedfrom the metal anode pad and/or the metal cathode pad, for exampleduring component singulation. The metal link may also comprise a fusiblemetal.

In still other embodiments, the metal anode pad and the metal cathodepad include curved facing surfaces. In some embodiments, the curvedfacing surfaces comprise a plurality of line segments that form obliqueand/or orthogonal angles therebetween. In other embodiments, the metalanode pad includes a metal finger that extends toward the metal cathodepad and the metal cathode pad includes a metal finger that extendstoward the metal anode pad.

Some of the embodiments described above that include facing surfacesthat comprise a plurality of line segments that form oblique and/ororthogonal angles therebetween may be used to mount more than one LEDdie in the plastic cup. For example, in some embodiments, the LED die isa first LED die disposed in the plastic cup such that the outer face ofthe anode contact is closely spaced apart from the metal anode padadjacent a first one of the line segments and the outer face of thecathode contact is closely spaced apart from the metal cathode padadjacent the first one of the line segments. The LED component furthercomprises a second LED die that also comprises first and second opposingfaces and an anode contact and a cathode contact on the first facethereof, the anode and cathode contacts including outer faces remotefrom the second LED die. The second LED die is also disposed in theplastic cup such that the outer face of the anode contact is closelyspaced apart from the metal anode pad adjacent a second one of the linesegments and the outer face of the cathode contact is closely spacedapart from the metal cathode pad adjacent the second one of the linesegments.

In yet other configurations of the metal pads, one of the metal anodepad or the metal cathode pad includes three edges and the other of themetal cathode pad or the metal anode pad extends adjacent the threeedges. In other embodiments, one of the metal anode pad or the metalcathode pad includes four edges and the other of the metal cathode pador the metal anode pad extends adjacent the four edges.

Various embodiments described above configure the metal anode pad, themetal cathode pad and/or the plastic cup to facilitate the directattachment of the LED die to the lead frame. In other embodiments, thedie attach layer itself is configured to facilitate the directelectrical connection of the outer face of the anode contact to theexposed portion of the metal anode pad and the direct electricalconnection of the outer face of the cathode contact to the exposedportion of the metal cathode pad by the die attach layer. Specifically,in some embodiments, the exposed portions of the metal anode and cathodepads deviate from coplanarity by a height difference, and the die attachlayer is thicker than the height difference. In other embodiments, thedie attach layer also may be thicker than 3 μm. In still otherembodiments, the die attach layer is of different thickness between theouter face of the anode contact that is closely spaced apart from theexposed portion of the metal anode pad compared to between the outerface of the cathode contact that is closely spaced apart from theexposed portion of the metal cathode pad.

Yet other embodiments may configure the composition of the die attachlayer to facilitate the direct electrical connection. Specifically, insome embodiments, the die attach layer comprises Gold (Au), Nickel (Ni)and Tin (Sn). In other embodiments, 0<Au wt %≦10, 10≦Ni wt %≦60 and40≦Sn wt %≦90. In yet other embodiments, 0.8≦Au wt %≦4.5, 19≦Ni wt %≦41and 55≦Sn wt %≦80.

In still other embodiments, the plastic cup comprises silicone and thedie attach material has a melting temperature below a decompositiontemperature of the silicone. In yet other embodiments, the die attachmaterial has a melting temperature below 260° C. Moreover, in otherembodiments, the die attach material has a melting temperature and has are-melting temperature that is higher than the melting temperature. Insome embodiments, the melting temperature is below 260° C. and there-melting temperature is above 260° C.

It will be understood that the various embodiments of configuring themetal anode pad, the metal cathode pad, the plastic cup and/or the dieattach layer that are described herein may be used together in variouscombinations or subcombinations, depending upon many factors, includingfactors related to the LED die, factors related to the lead frame,factors related to the overall LED component and/or the application forwhich the LED component is intended. In one example, the deviation fromcoplanarity that is provided by an LED package may dictate which of theabove-described configurations of the metal anode pad, the metal cathodepad, the plastic cup and/or the die attach layer are used.

Various embodiments described above have described LED components.However, other embodiments described herein may provide a lead frameitself or an LED itself.

Specifically, a lead frame according to various embodiments describedherein, may include a metal anode pad and a metal cathode pad, and aplastic cup on the metal anode pad and the metal cathode pad thatdefines an exposed portion of the metal anode pad and an exposed portionof the metal cathode pad in the plastic cup. The metal anode pad, themetal cathode pad and/or the plastic cup are configured to facilitate adirect solder connection of respective anode and cathode contacts of aLight Emitting Diode (LED) die to the respective exposed portion of themetal anode pad and the exposed portion of the metal cathode pad. Themetal anode pad, the metal cathode pad and/or the plastic cup may beconfigured according to any and all of the embodiments described herein.

Similarly, an LED according to various embodiments described herein mayinclude an LED die that comprises first and second opposing faces and ananode contact and a cathode contact on the first face thereof, the anodeand cathode contacts including outer faces remote from the LED die, anda die attach layer on the outer faces of the anode contact and thecathode contact. The die attach layer is configured to facilitate directattachment of the die attach layer to metal anode and cathode pads of alead frame. The die attach layer may be configured to facilitate directattachment according to any and all of the embodiments described herein.

Methods of fabricating an LED component may also be provided accordingto various embodiments described herein. These methods may compriseproviding a lead frame that comprises a metal anode pad, a metal cathodepad and a plastic cup on the metal anode pad and the metal cathode padthat defines an exposed portion of the metal anode pad and an exposedportion of the metal cathode pad in the plastic cup, and providing anLED die that comprises first and second opposing faces, an anode contactand a cathode contact on the first face thereof, and a die attach layeron outer faces of the anode and cathode contacts remote from the LEDdie. The LED die is placed in the cup such that the die attach layer isdirectly on the exposed portion of the metal anode pad and the exposedportion of the metal cathode pad. The die attach layer is then melted sothat the die attach layer directly electrically connects the outer faceof the anode contact to the exposed portion of the metal anode pad anddirectly electrically connects the outer face of the cathode contact tothe exposed portion of the metal cathode pad. The lead frame and/or dieattach layer may be configured according to any and all of theembodiments described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an LED die according to variousembodiments described herein.

FIG. 2A is a cross-sectional view of an LED component including an LEDdie that is directly attached to a lead frame according to variousembodiments described herein.

FIG. 2B is a top view of the LED component of FIG. 2A.

FIG. 3 is a cross-sectional view of an LED component including an LEDdie that is directly attached to a lead frame according to various otherembodiments described herein.

FIG. 4 is a cross-sectional view of an LED component including an LEDdie that is directly attached to a lead frame according to yet otherembodiments described herein.

FIGS. 5-11 are bottom views of a lead frame according to variousembodiments described herein.

FIG. 12 and FIGS. 13A-13B, which may be collectively referred to hereinas FIG. 13, are top views of an LED lead frame with one or more LED diesthereon according to various embodiments described herein.

FIG. 14 is a bottom view of a lead frame according to various otherembodiments described herein.

FIG. 15 is a top view of an LED lead frame with one or more LED diesthereon according to various other embodiments described herein.

FIG. 16 is a bottom view of a lead frame according to still otherembodiments described herein.

FIGS. 17A-17C, which may be collectively referred to herein as FIG. 17,are top views of an LED lead frame with one or more LED dies thereonaccording to still other embodiments described herein.

FIG. 18 is a cross-sectional view of an LED component including an LEDdie that is directly attached to a lead frame according to yet otherembodiments described herein.

FIG. 19 is a cross-sectional view of an LED die according to variousembodiments described herein.

FIG. 20 is a cross-sectional view of a conventional LED die.

FIG. 21 is a cross-sectional view of an LED die according to variousembodiments described herein.

FIG. 22 is a phase diagram illustrating performance of die attachmaterials according to various embodiments described herein duringmelting and re-melting.

FIG. 23 is a flowchart of operations that may be performed to fabricateLED components according to various embodiments described herein.

FIG. 24 illustrates a lead frame structure that can be used to fabricatea plurality of LED components, according to various embodimentsdescribed herein.

DETAILED DESCRIPTION

Various embodiments of the inventive concepts now will be described morefully with reference to the accompanying drawings. The inventiveconcepts may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the inventive conceptsto those skilled in the art. In the drawings, the size and relativesizes of layers and regions may be exaggerated for clarity. Like numbersrefer to like elements throughout.

It will be understood that when an element such as a layer, region orsubstrate is referred to as being “on” another element, it can bedirectly on the other element or intervening elements may also bepresent. Furthermore, relative terms such as “beneath” or “overlies” maybe used herein to describe a relationship of one layer or region toanother layer or region relative to a substrate or base layer asillustrated in the figures. It will be understood that these terms areintended to encompass different orientations of the device in additionto the orientation depicted in the figures. The term “directly” meansthat there are no intervening elements. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items and may be abbreviated as “/”.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting to otherembodiments. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes”, “including”, “have” and/or“having” (and variants thereof) when used herein, specify the presenceof stated features, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,steps, operations, elements, components, and/or groups thereof.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Various embodiments are described herein with reference tocross-sectional and/or other illustrations that are schematicillustrations of idealized embodiments. As such, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, theseembodiments should not be construed as limited to the particular shapesof regions illustrated herein but are to include deviations in shapesthat result, for example, from manufacturing. For example, a regionillustrated or described as a rectangle will, typically, have rounded orcurved features due to normal manufacturing tolerances. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the precise shape of a region of adevice and are not intended to limit the scope of the inventiveconcepts, unless otherwise defined herein.

Unless otherwise defined herein, all terms (including technical andscientific terms) used herein have the same meaning as commonlyunderstood by one of ordinary skill in the art to which this inventionbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand this specification and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Some embodiments now will be described generally with reference togallium nitride (GaN)-based light emitting diodes on silicon carbide(SiC)-based growth substrates for ease of understanding the descriptionherein. However, it will be understood by those having skill in the artthat other embodiments of the present invention may be based on avariety of different combinations of growth substrate and epitaxiallayers. For example, combinations can include AlGaInP diodes on GaPgrowth substrates; InGaAs diodes on GaAs growth substrates; AlGaAsdiodes on GaAs growth substrates; SiC diodes on SiC or sapphire (Al₂O₃)growth substrates and/or a Group III-nitride-based diode on galliumnitride, silicon carbide, aluminum nitride, sapphire, zinc oxide and/orother growth substrates. Moreover, in other embodiments, a growthsubstrate may not be present in the finished product. For example, thegrowth substrate may be removed after forming the light emitting diode,and/or a bonded substrate may be provided on the light emitting diodeafter removing the growth substrate. In some embodiments, the lightemitting diodes may be gallium nitride-based LED devices manufacturedand sold by Cree, Inc. of Durham, N.C.

Introduction

Various embodiments described herein can provide an LED component thatcomprises an SMD lead frame and an LED that is electrically connected tothe SMD lead frame without wire bonds. More specifically, one or both ofthe LED contacts is directly attached to the SMD lead frame using a dieattach layer, such as solder.

Various embodiments described herein may arise from recognition that SMDLEDs using lead frame technology have the potential advantage of verylow cost. Yet, heretofore, at least one of the LED die contacts, and inmany cases both of the LED die contacts, were connected to the SMD leadframe using one or more wire bonds. Wire bonds can compensate for thedeviation from flatness and the high degree of mechanical flex in lowcost SMD lead frames. This deviation from flatness and mechanical flexmay only increase as lower cost plastics, such as silicone, are used forthe lead frame cup.

Yet, various embodiments described herein have recognized that theconfiguration of the metal anode pad, the metal cathode pad and/or theplastic cup of the SMD LED lead frame, and/or the configuration of thedie attach material, can be changed, so as to allow the elimination ofwire bonding in the SMD LED component and allow direct attachment ofboth the anode and cathode contacts of the LED die to the respectivemetal anode pad and cathode pad of the lead frame using a die attachlayer, such as solder. The direct die attachment can be lower cost andmore robust than wire bonding and can also allow more compact SMDcomponents.

Many techniques will be described below for configuring the metal anodepad, the metal cathode pad, the plastic cup and/or the die attach layer,to facilitate direct attachment of an LED die to an SMD lead framewithout wire bonds. However, having recognized the breakthrough that anLED die can be electrically connected to the SMD lead frame without wirebonds, many other configurations may be envisioned by those of skill inthe art.

FIG. 1 is a cross-sectional view of a Light Emitting Diode (LED) die,also referred to as an LED chip, according to various embodimentsdescribed herein. Referring to FIG. 1, the LED die 100 includes a dioderegion 110 having first and second opposing faces 110 a, 110 b,respectively, and including therein an n-type layer 112 and a p-typelayer 114. Other layers or regions may be provided, which may includequantum wells, buffer layers, etc., that need not be described herein.An anode contact 160 ohmically contacts the p-type layer 114 and extendson the first face 110 a. The anode contact 160 may directly ohmicallycontact the p-type layer 114, or may ohmically contact the p-type layer114 by way of one or more conductive vias 162 and/or other intermediatelayers. A cathode contact 170 ohmically contacts the n-type layer 112and also extends on the first face 110 a. The cathode contact 170 maydirectly ohmically contact the n-type layer 112, or may ohmicallycontact the n-type layer 112 by way of one or more conductive vias 172and/or other intermediate layers. As illustrated in FIG. 1, the anodecontact 160 and that cathode contact 170 that both extend on the firstface 110 a are coplanar, although they need not be coplanar. The dioderegion 110 also may be referred to herein as an “LED epi region”,because it is typically formed epitaxially on a substrate 120. Forexample, a Group III-nitride based LED epi region 110 may be formed on asilicon carbide growth substrate. In some embodiments, the growthsubstrate may be present in the finished product. In other embodiments,the growth substrate may be removed. In still other embodiments, anothersubstrate may be provided that is different from the growth substrate.

As also shown in FIG. 1, a die attach layer 180 is also provided on theouter face of the anode contact 160 and on the outer face of the cathodecontact 170. As will be described in detail below, the die attach layer180 may be configured to facilitate direct attachment of the LED die toan SMD lead frame.

As also shown in FIG. 1, a transparent substrate 120, such as atransparent silicon carbide growth substrate, is included on the secondface 110 b of the diode region 110. The transparent substrate 120includes a sidewall 120 a and may also include an inner face 120 cadjacent the second face 110 b of the diode region 110 and an outer face120 b, remote from the inner face 120 c. The outer face 120 b may be ofsmaller area than the inner face 120 c. In some embodiments, thesidewall 120 a may be stepped, beveled and/or faceted, so as to providethe outer face 120 b that is of smaller area than the inner face 120 c.In other embodiments, as shown in FIG. 1, the sidewall is an obliquesidewall 120 a that extends at an oblique angle, and in some embodimentsat an obtuse angle, from the outer face 120 b towards the inner face 120c. In yet other embodiments, the sidewall 120 a may be orthogonal to thefaces. Moreover, the LED die 100 may include a layer comprisingluminophoric material, such as phosphor, on at least some of the outersurfaces thereof. The layer may extend on the outer face 120 b, on thesidewall 120 a and/or on the side of the diode region 110, and may beconformal and/or nonconformal to the surface on which it extends. Yetother optical and/or protective layers may be provided on the LED die.

LED dies 100 configured as was described above in connection with FIG.1, may be referred to as “horizontal” or “lateral” LEDs, because boththe anode and the cathode contacts thereof are provided on a single faceof the LED die. Horizontal LEDs may be contrasted with vertical LEDs inwhich the anode and cathode contacts are provided on opposite facesthereof.

Various other configurations of horizontal LEDs that may be usedaccording to any of the embodiments described herein, are described indetail in U.S. Pat. No. 8,368,100 to Donofrio et al., entitled“Semiconductor Light Emitting Diodes Having Reflective Structures andMethods of Fabricating Same”; U.S. Patent Application Publication2011/0031502 to Bergmann et al., entitled “Light Emitting DiodesIncluding Integrated Backside Reflector and Die Attach”; U.S. PatentApplication Publication 2012/0193660 to Donofrio et al. entitled“Horizontal Light Emitting Diodes Including Phosphor Particles”; andU.S. Patent Application Publication 2012/0193662 to Donofrio et al.entitled “Reflective Mounting Substrates for Flip-Chip MountedHorizontal LEDs”, assigned to the assignee of the present application,the disclosures of which are hereby incorporated herein by reference intheir entirety as if set forth fully herein.

Other configurations of horizontal LEDs may be embodied by the “DirectAttach” LED chips that are marketed by Cree, Inc., the assignee of thepresent application, and which are described, for example, in DataSheets entitled “Direct Attach DA2432™ LEDs” (Data Sheet: CPR3FM Rev.-,2011); “Direct Attach DA1000™ LEDs” (Data Sheet: CPR3ES Rev. A, 2010);and “Direct Attach DA3547™ LEDs” (Data Sheet: CPR3EL Rev. D, 2010-2012),the disclosures of which are hereby incorporated herein by reference intheir entirety as if set forth fully herein.

In order to simplify the drawings which follow, the internal structureof LED dies 100 will not be illustrated. Rather, the following figureswill illustrate the LED die 100 schematically, but will illustrate anodecontact 160, cathode contact 170 and die attach layer 180. Since the dieattach layer may be modified according to various embodiments describedherein, it will be labeled 180′. The LED die 100 comprises first andsecond opposing faces, wherein the first opposing face is the first face110 a of the diode region and the second face is the second face 110 bof the diode region when no substrate is present, or the outer face 120b of the substrate 120 when a substrate 120 is present. The anodecontact 160 and the cathode contact 170 are on the first face 110 a.

Moreover, in various embodiments described herein, all of the LED dies100 may be illustrated as being of the same size and generallyrectangular or square. However, the LED dies 100 may be of other shapes,and need not all be the same size or type of LED die. Moreover, theanode and cathode contacts 160 and 170, respectively, are allillustrated as being different in size. In other embodiments, however,the anode and/or cathode contacts of the various LED may be of the samesize, shape and/or thickness, and/or the anode and/or cathode contactsof the various LEDs need not be the same size, shape and/or thickness asone another. The LED dies 100 may emit different colors of light and mayinclude a luminophoric layer, such as phosphor layer thereon. Forexample, in some embodiments, a combination of white (for example, blueshifted yellow) and red LED dies may be provided. Moreover, any numberof multiple LED dies 100 may be provided based on the requirements ofthe LED component.

Direct Attach SMD LED Components

FIG. 2A is a cross-sectional view, and FIG. 2B is a top view, of an LEDcomponent according to various embodiments described herein. Referringto FIGS. 2A and 2B, the LED component 200 comprises a lead frame 210that itself includes a metal anode pad 220, a metal cathode pad 230 anda plastic cup 240 on the metal anode pad 220 and the metal cathode pad230 that defines an exposed portion 220 e of the metal anode pad 220 andan exposed portion 230 e of the metal cathode pad 230 in the plastic cup240. The LED component 200 also includes an LED die 100 that comprisesfirst and second opposing faces 110 a, 120 b, respectively, and an anodecontact 160 and a cathode contact 170 on the first face 110 a thereof.The anode and cathode contacts 160 and 170 include outer faces 160 o,170 o, respectively, remote from the LED die 100. The LED die 100 isdisposed in the plastic cup 240, such that the outer face 160 o of theanode contact 160 is closely spaced apart from the exposed portion 220 eof the metal anode pad 220 and the outer face 170 o of the cathodecontact 170 is closely spaced apart from the exposed portion 230 e ofthe metal cathode pad 230.

The LED component 200 also includes a die attach layer 180′ that extendsbetween the outer face 160 o of the anode contact 160 and the exposedportion 220 e of the metal anode pad 220, and also extends between theouter face 170 o of the cathode contact 170 and the exposed portion 230e of the metal cathode pad 230. Moreover, the die attach layer 180′directly electrically connects the outer face 160 o of the anode contact160 to the exposed portion 220 e of the metal anode pad 220, and alsodirectly electrically connects the outer face 170 o of the cathodecontact 170 to the exposed portion 230 e of the metal cathode pad 230.

The metal anode pad 220 and the metal cathode pad 230 may be part of alarger metal lead frame structure that is singulated after componentmanufacture, as will be described in detail below. The metal lead framestructure may comprise a patterned flat plate of copper, copper alloyand/or other conductive metal. It will also be understood that althoughthe metal anode pad 220 and the metal cathode pad 230 are shown as asingle layer, multiple layer pads may also be provided. For example, areflective coating may be provided on all or part of the exposedportions 220 e, 230 e and/or on other portions of the surface of themetal anode pad 220 and metal cathode pad 230 that face the LED die 100,to enhance reflectivity of any light that is emitted by the LED thatdirectly or indirectly impinges on the surface of the metal anode pad220 and/or the metal cathode pad 230. Moreover, although the metal anodepad 220 and the metal cathode pad 230 are illustrated as extendingbeyond the plastic cup 240, they need not do so. Finally, it will beunderstood that the metal anode pad 220 and the metal cathode pad 230may be of the same size, shape and/or thickness, or may be differentsize, shape and/or thickness.

The plastic cup 240 may comprise a plastic. As used herein, a “plastic”is any of a wide range of synthetic or semi-synthetic organic solidsthat are moldable. Plastics are typically organic polymers of highmolecular mass, but they often contain other substances. In someembodiments, the plastic cup 240 may comprise polyphthalamide (PPA),which is a thermoplastic synthetic resin of the polyamide (nylon)family, and which has a relatively high melting point of between 290° C.and 305° C. In other embodiments, the plastic cup 240 may comprisepolycyclohexylenedimethylene terephthalate (PCT), which is athermoplastic polyester that also may have a melting point of between290° C. and 305° C. In other embodiments, the plastic cup 240 maycomprise an Epoxy Molding Compound (EMC), which are flexible epoxyresins which may have a melting point of between 270° C. and 280° C.Moreover, present-day and future plastic cups 240 may comprise siliconesof varied compositions and which may have a decomposition temperature of350° C. Silicones are polymers that include silicon together withcarbon, hydrogen, oxygen and/or other elements. As understood by thosehaving skill in the art, some silicones may not actually melt. Rather,they may be decomposed, for example by charring, off-gassing, etc. Thisdecomposition may begin at 350° C., but this decomposition temperaturemay vary depending upon the silicone that is used. Other silicones maydecompose and melt at the same temperature. Yet other silicones may havea melting temperature that is higher than the decomposition temperature.Yet other plastic materials may be used.

Moreover, at least some portion of the plastic cup 240 may betransparent, translucent and/or opaque. The plastic cup 240 also neednot be uniform in construction, so that is may include various portionsthat are transparent, translucent or opaque, and other portions that arenot transparent, translucent or opaque. Additional materials may also beadded in the plastic cup, for example to enhance the reflectancethereof, to provide optical scattering and/or to provide wavelengthconversion. It will also be understood that the plastic cup 240 may bemolded on the metal anode and cathode pads 220 and 230, respectively,after LED die attach, rather than before LED die attach as describedherein.

The plastic cup 240 may comprise a plastic cup wall 240W that is on themetal anode pad 220 and the metal cathode pad 230, and extends away fromthe metal anode pad 220 and the metal cathode pad 230, to define acavity or recess therein in which the LED die 100 is disposed. Theplastic cup wall 240W may be of uniform thickness, or variable thicknessas illustrated in FIG. 2A, and may include various protrusions, bulgesor recesses therein. A cup base 240B may generally extend in thedirection of the metal anode pad 220 and metal cathode pad 230, and mayalso extend on either face of the metal anode pad 220 and/or metalcathode pad 230. The outer edge of the cup base 240B may be wider and/ornarrower than the outer edge of the cup wall 240W, or may be congruentthereto. Moreover, the outer edge of the cup base 240B may have adifferent shape than the outer edge of the cup wall 240W.

The die attach layer 180′ may comprise a lead-based or lead-free solder.Moreover, according to various embodiments described herein, a ternarysolder that comprises gold (Au), nickel (Ni) and tin (Sn) may also beused. Quaternary (or other) variations of this solder may also beprovided, as will be described in detail below. The die attach layer180′ may be fabricated using deposition and/or other conventionaltechniques.

Finally, FIG. 2A also illustrates an encapsulant 250 in, and in someembodiments filling, the interior of the plastic cup 240. In someembodiments, the encapsulant 250 may also include silicone, which may bethe same composition and/or a different composition than that of theplastic cup 240. The encapsulant 250 may be uniform or non-uniform incomposition, and may include optical materials therein, such as indexmatching, scattering, reflecting and/or wavelength conversion materialssuch as phosphor, that may be uniformly or non-uniformly distributedtherein. The outer surface of the encapsulant 250 may be flush with theouter surface of the plastic cup 240, as illustrated in FIG. 2A.However, in other embodiments, the outer surface of the encapsulant maybe dished or domed relative to the outer surface of the cup 240.Moreover, various optical features such as macro lenses and/ormicrolenses may be provided in and/or on the outer surface of theencapsulant 250.

FIGS. 2A and 2B may also be regarded as illustrating an LED componentaccording to various embodiments described herein that comprises an SMDlead frame 210 and an LED die 100 that is electrically connected to theSMD lead frame 210 without wire bonds. In some embodiments, the SMD leadframe 210 comprises a plastic cup 240 and the LED die 100 is in theplastic cup 240 and is electrically connected to the SMD lead frame 210in the plastic cup 240. In some embodiments, the LED die 100 is solderedto the SMD lead frame 210, for example using the die attach layer 180′.

FIGS. 2A and 2B also illustrate a surface mount device lead frameaccording to various embodiments described herein. The surface mountdevice lead frame 210 comprises a metal anode pad 220 and a metalcathode pad 230. A plastic cup 240 is provided on the metal anode pad220 and the metal cathode pad 230 that defines an exposed portion 220 eof the metal anode pad 220 and an exposed portion 230 e of the metalcathode pad 230. The metal anode pad 220, the metal cathode pad 230and/or the plastic cup 240 are configured to facilitate direct solderattachment of anode and cathode contacts 160 and 170, respectively, ofan LED die 100 to the respective exposed portions 220 e, 230 e of themetal anode pad 220 and the metal cathode pad 230. In some embodiments,the plastic cup 240 is not included in the lead frame 210.

FIGS. 2A and 2B also illustrate a surface mount device LED thatcomprises an LED die 100 having first and second opposing faces 110 a,120 b, respectively, and an anode contact 160 and a cathode contact 170on the first face 110 a thereof. The anode and cathode contacts 160 and170 include outer faces 160 o, 170 o, respectively, remote from the LEDdie 100. A die attach layer 180′ is provided on the outer faces 160 o,170 o of the anode contact 160 and the cathode contact 170. The dieattach layer 180′ is configured to facilitate direct attachment of thedie attach layer 180′ to anode and cathode pads 220, 230, respectively,of an SMD lead frame 210.

In FIG. 2A, the plastic cup 240 is only on the exposed surface 220 e,230 e of the metal anode pad 220 and metal cathode pad 230. However, asillustrated in FIG. 3, the plastic cup base 240B may also extend on thesurfaces of the metal anode pad 220 and the metal cathode pad 230opposite the exposed surfaces 220 e, 230 e. Moreover, as shown in FIG.4, the plastic cup base 240B may extend in a continuous manner on thesurfaces of the metal anode pad 220 and metal cathode pad 230 that areopposite the exposed surfaces 220 e, 230 e thereof. Moreover, in someembodiments, the metal anode pad 220 and the metal cathode pad 230 maybe bent around the plastic cup 240B to provide external contacts for theLED component 200. Many other variations of lead frames 210 may beprovided according to various embodiments described herein. For example,some embodiments of a lead frame 210 may not include a plastic cup 240.

According to various embodiments that will now be described in detail,the metal anode pad 220, the metal cathode pad 230, the plastic cup 240and/or the die attach material 180′ may be configured to facilitate thedirect electrical connection of the outer face 160 o of the anodecontact 160 to the exposed portion 220 e of the metal anode pad 220, andthe direct electrical connection of the outer face 170 o of the cathodecontact 170 to the exposed portion 230 e of the metal cathode pad 230,by the die attach layer 180′. Various structural and compositionalconfigurations will now be described. It will be understood that theseconfigurations may be varied in combination or in varioussubcombinations to achieve a desired LED component yield from thestandpoint of performance and/or reliability. The individual aspects ofthe configuration of the metal anode pad 220, metal cathode pad 230,plastic cup 240 and/or die attach layer 180′ that are selected willdepend on the particular LED die 100 and/or lead frame 240 that is beingused, and/or the particular cost, reliability and/or performance that isdesired. However, by configuring the metal anode pad 220, the metalcathode pad 230, the plastic cup 240 and/or the die attach material 180′according to various embodiments described herein and/or otherconfigurations that may be developed by those having skill in the art,direct attachment of an LED die 100 to a surface mount lead frame 210without wire bonds may be achieved.

In general, lead frames may provide low cost alternatives to ceramicsubmounts that are conventionally used in LED components. Moreover, leadframes have good thermal conductivity, since the package floor can bealmost all metal. Stated differently, the LED die are bonded to themetal, which is in turn soldered to a board, so as to provide lowthermal resistance. Lead frames can run on SMD package lines that tendto be cheaper and more depreciated with less expensive tools. As but oneexample, lead frames may not require a mechanical saw to singulateindividual components, but, rather, may use a cheaper punch technologythat has lower capital investment and lower consumption cost compared toconventional ceramic packages.

Unfortunately, however, lead frames may have poor reliability when theyare made out of PPA, PCT, or EMC, as compared to ceramic. SMD leadframes also may be less flat than ceramic, which makes attaching LEDdies a challenge. Lead frames also are generally not temperature-stableup to the reflow temperature of conventional gold-tin eutectic solders,so that upon reflow the packages may tend to darken. Recent advancementsin silicone-based lead frames may provide better reliability and canwithstand a higher reflow temperature. However, silicone-based leadframes tend to be flimsy and flexible. As such, while the metal anodeand cathode pads may be generally coplanar, they are not perfectlycoplanar, and generally are not flat enough to allow direct die attachof both the anode and cathode contacts of an LED die.

Various embodiments that will now be described can allow the metal anodepad 220, metal cathode pad 230, plastic cup 240 and/or die attachmaterial 180′ to be configured, so as to allow a lead frame 210, andparticularly a silicone-based lead frame 210, to work with a directattach LED die 100, to provide a path for high volume, low cost andreliable LED components.

In the following sections, various configurations of the metal anode pad220, metal cathode pad 230 and plastic cup 240 will first be described.Then, various configurations of the die attach layer 180′ will bedescribed.

Configuring the Metal Anode Pad, the Metal Cathode Pad and/or thePlastic Cup

Various embodiments will now be described that can configure the metalanode pad 220, the metal cathode pad 230 and/or the plastic cup 240 ofthe lead frame 210, to facilitate the direct electrical connection ofthe outer face 160 o of the anode contact 160 to the exposed portion 220e of the metal anode pad 220, and the direct electrical connection ofthe outer face 170 o of the cathode contact 170 to the exposed portion230 e of the metal cathode pad 230, by the die attach layer 180′. Ingeneral, the metal anode pad 220, metal cathode pad 230 and/or plasticcup 240 may be configured according to various embodiments describedherein by (a) increasing an extension of the cup base relative to a gapbetween the metal anode and cathode pads; (b) providing temporary linksbetween the metal anode and cathode pads; and/or (c) providing a curvedfacing surfaces between the metal anode and cathode pads. Each of theseconfigurations may be designed to reduce the deviation from planarity ofthe anode and cathode pads. Each of these configurations will now bedescribed in detail.

(a) Increasing an Extension of the Cup Base Relative to a Gap Betweenthe Metal Anode and Cathode Pads

According to various embodiments that will now be described, adjacentends of the metal anode pad and the metal cathode pad define a gaptherebetween. The plastic cup extends in the gap and also extends beyondnon-adjacent ends of the metal anode pad and the metal cathode pad by adistance. The distance is larger than the gap. The plastic cup may beconfigured to extend in the gap and beyond the non-adjacent ends duringthe molding process that forms the plastic cup.

More specifically, FIG. 5 is a simplified bottom view of a lead frame210 of FIGS. 2A and 2B. As illustrated in FIG. 5, adjacent ends 220 a,230 a of the metal anode pad 220 and the metal cathode pad 230,respectively, define a gap G therebetween. Moreover, the base 240B ofthe plastic cup 240 extends in the gap G. The base 240B of the plasticcup 240 also extends beyond non-adjacent ends 220 n, 230 n of the anodeand cathode pads 220, 230, respectively, by a distance D. According tovarious embodiments described herein, the distance D is larger than thegap G.

Conventionally, the distance D is minimized in order to decrease theoverall size of the LED component and allow more components per leadframe and per resin load, to thereby allow lower cost to be achieved.However, according to various embodiments described herein, the distanceD is configured to be larger than the gap G. In other embodiments, athicker cup wall 240W also may be provided, that is thicker than the gapG.

Without wishing to be bound by any theory of operation, it has beenfound that the rigidity of the lead frame 210 shown in FIG. 5 can beincreased and/or a deviation from planarity of the adjacent ends 220 a,230 a of the anode and cathode pads 220, 230 may be reduced, byproviding a larger distance D and/or a thicker cup wall 240W. Asdescribed above, in some embodiments, the distance D is larger than thegap G. In other embodiments, the distance D is at least 10% larger thanthe gap G. In yet other embodiments, the distance D is at least 30%larger than the gap G. Thus, embodiments of FIG. 5 increase the ratiobetween the extension distance D and the gap G. This increase in ratiocan provide a more rigid framework, which can allow for a higher rate ofsuccessful die attach on the lead frame material due to an increase inoverall structural rigidity. This may be the case even when flexiblesilicone is used for the cup 240.

It will also be understood that various embodiments of FIG. 5 may leadto a slight decrease in thermal performance of the LED component becausethe metal anode and cathode pads 220, 230 occupy a smaller percentage ofthe overall width of the component. This slight decrease in thermalperformance may not present an undue disadvantage, because the thermalperformance of lead frames, and especially of LED dies that are dieattached to the lead frame rather than wire bonded to the lead frame,may be more than adequate to ensure good thermal performance.

In a particular example, the gap G may have a width of between 100 μm to200 μm, and the distance D may be greater than 220 μm in someembodiments, greater than 300 μm in other embodiments, and greater than400 μm in yet other embodiments. In some embodiments, the distance Ddoes not exceed 1,000 μm. In other embodiments, when thermal performanceis of greater concern than mechanical rigidity, the distance D may bemade less than the gap G, as illustrated in FIG. 6.

It will also be understood that the distance D need not be greater thanor less than the gap G throughout the LED component 200. Rather, thisrelationship may only be present over some of the non-adjacent ends 220n, 230 n, or may only be present over portions of the non-adjacent ends220 n, 230 n. Stated differently, the gap G may be of nonuniform widthover the extent thereof, and the distance D need not be uniform over theextent thereof. Moreover, the distance D need not be the same adjacenteach of the non-adjacent ends 220 n of the metal anode pad 220 and/oradjacent each of the non-adjacent ends 230 n of the metal cathode pad230.

FIG. 7 illustrates other embodiments wherein different ratios of thedistance D to the gap G may be provided in a single component, in orderto allow potential benefits of better thermal properties as well ashigher package rigidity or stability. For example, in FIG. 7, twodifferent ratios of the distance D1 for the metal anode pad 220 relativeto the gap G and the distance D2 of the metal cathode pad 230 relativeto the gap G may be provided.

Various embodiments described in connection with FIG. 7 may arise fromrecognition that one of the metal pads, such as the metal cathode pad230, may be larger than the other of the metal pads, such as the metalanode pad 220, which can provide better thermal performance for thislarger metal cathode pad 230. In contrast, the other metal pad, such asthe metal anode pad 220, may be less important for thermal performance,so that its width may be decreased so as to provide a larger distance D1for stability. It will be understood that, in the above description, theroles of the metal anode pad 220 and the metal cathode pad 230 may bereversed.

Thus, FIG. 7 illustrates various embodiments described herein, whereinthe adjacent ends 220 a and 230 a, respectively, of the metal anode pad220 and the metal cathode pad 230 have different widths. It will also beunderstood that, in some embodiments, multiple LED dies are providedwithin a single plastic cup. In these embodiments, different gaps anddifferent distances may be provided for at least some of the multipleLED dies in the plastic cup.

The different widths of the adjacent ends 220 a and 230 a, respectively,of the metal anode pad 220 and the metal cathode pad 230 may also beachieved by selectively covering portions of the metal anode pad 220and/or the metal cathode pad 230 with the plastic material from the cupbase 240B. Thus, in some embodiments, the cup base 240B may form a ridgeon one or both of the opposing faces of the metal anode pad 220 and/orthe metal cathode pad 230. This ridge may also at least partially clampthe metal anode pad 220 and/or the metal cathode pad 230, and therebyreduce deviation from planarity. For example, as was illustrated in FIG.3 and/or FIG. 4, the plastic cup base 240B may extend on the oppositefaces of the metal anode pad 220 and/or the metal cathode pad 230. Thismay provide a ridge on the pad(s) and may further clamp the pad(s) toincrease coplanarity. Moreover, by allowing the base 240B of the plasticcup 240 to extend on the outer surface of the metal anode pad 220 and/orthe metal cathode pad 230, the lead frame package designer can customdesign the backside appearance and functionality of the LED component.

Various embodiments of FIGS. 5-7 can increase the stability and otherbeneficial physical properties, such as thermal conductivity, of leadframe-style packages that are used with direct-attach LED dies bymodifying the width ratio between the cup base and/or wall thickness andthe gap between the metal pads on the back of the lead frame. Anincrease in the ratio between the thickness and the gap can lead to amore rigid lead frame, allowing for a higher rate of successful dieattach on the lead frame material due to an increase in overallstructural rigidity. A lower ratio between the thickness and the gap canlead to a more flexible package with better thermal parameters due tothe increased thermal mass on the bottom of the package. Conventionally,packages have narrow cup walls with dominant metal pads on the back ofthe lead frame package.

(b) Providing Temporary Links Between the Metal Anode and Cathode Pads

According to various other embodiments described herein, the planarityof the metal anode pad and metal cathode pad may be increased, so as tofacilitate die attach without wire bonding, by providing temporary linksthat mechanically connect the metal anode pad to the metal cathode padoutside the plastic cup. These temporary links can increase thestructural rigidity of the metal anode and the metal cathode pad duringdie attach. The temporary links can be severed during and/or aftersingulation of the individual components, after die attach.

More specifically, referring to FIG. 8, a lead frame 210 may include oneor more metal links 810 that mechanically connect the metal anode pad220 to the metal cathode pad 230 outside the plastic cup base 240B. Themetal links 810 may be provided as part of the initial lead framestructure that is used to fabricate a large number of LED components.The metal links 810 are only temporary because they would short circuitthe LED if they remained in the finished product. Thus, duringsingulation, which separates the individual LED components from theinitial lead frame structure, the metal links 810 may be severed alongwith any other temporary links that link the individual anode andcathode metal pads 220, 230 to the initial lead frame structure.Alternatively, they may be severed prior to or after singulation. Itwill be understood that fewer or more links 810 may be provided andvarious configurations of links may be provided. For example, althoughU-shaped links 810 are illustrated in FIG. 8, other shapes may beprovided.

FIG. 9 illustrates the LED component of FIG. 8 after singulation. Notethe LED has not been illustrated for clarity. The portions of the links810 outside the plastic cup 240 have been removed, but tabs 910 remain.These tabs 910 may provide an indication that a link 810 was used duringfabrication of the LED component to provide higher stability, accordingto various embodiments described herein.

Accordingly, FIGS. 8 and 9 illustrate various embodiments describedherein wherein out-of-cup connecting links or legs may be used toincrease the package stability and rigidity of lead frame-style packagesfor direct attach LED die components. Conventionally, the metal anodeand cathode contact pads may essentially float, with their edgesencapsulated in the cup material. In sharp contrast, embodiments of FIG.8 provide metal connecting links or legs outside the package edge. Theselinks can help to lock the pads to the same height, i.e., to increaseplanarity, and add package rigidity. As shown in FIG. 9, at packagesingulation, the connecting links or legs can be sheared to produce afinished package. The shearing may also sever indirect connections ofthe metal anode and cathode pads to the remainder of the lead frame.

FIG. 10 illustrates other embodiments wherein the metal link 810includes a fusible metal portion 1010. For example, any metal alloy orpure metal with a melting point below a decomposition temperature of theplastic cup may be used. This can allow for fast shear by locallyheating the connecting links 810 above the melting point of the fusibleportion 1010. Laser heating and/or other local heating techniques may beused. Global heating may also be used if the appropriate fusiblematerial is selected. It will also be understood that the fusiblematerial may extend to all of the link 810, to all of the link 810 thatis outside the plastic cup 240 and/or may only correspond to a smallportion of the metal link 810 outside the plastic cup 240 that issufficient to open the link. In other embodiments, the fusible link 1010may be inside the cup, as long as it is accessible to melting by a laserand/or other technique. Thus, the cup material may be molded around afusible metal link in the interior of the cup, so that the link can bemelted using a laser and/or other technique.

It will also be understood that the configuration and position of themetal link(s) may be varied according to various embodiments describedherein. For example, the arms of the link 810 may be closer to oneanother and may be closer to the gap between the metal anode pad 220 andthe metal cathode pad 230 than is illustrated in FIGS. 8-10, so as toincrease the structural rigidity of the adjacent ends 230 a, 230 a ofthe metal anode and cathode contacts 220, 230, respectively. Moreover,the link(s) 810 can be sheared at the package edge (leaving no extrametal exposed outside the lead frame package, as was illustrated in FIG.9) and/or outside the package (leaving metal exposed outside the packagefor contact points, thermal sinks and/or other purposes as illustrated,for example, in FIG. 10).

(c) Providing Curved Facing Surfaces Between the Metal Anode and CathodePads

Various embodiments that were described above in connection with FIGS.5-10 illustrated a gap G between the adjacent ends 220 a, 230 a,respectively, of the metal anode pad and the metal cathode pad 220, 230,respectively, that extended in a straight line along the adjacent ends220 a, 230 a. Stated differently, straight facing surfaces 220 a, 220 bof the metal anode and cathode pads 220, 230, respectively, wereillustrated. According to various embodiments that now will bedescribed, curved facing surfaces may be provided. The curved facingsurfaces may include smoothly curved and/or segmented portions. Thecurved facing surfaces can provide a greater length of cup materialalong the gap and can thereby provide more structural rigidity thanstraight facing surfaces that minimize the length of the cup material inthe gap. In some embodiments, the curved facing surfaces comprise aplurality of line segments that form oblique and/or orthogonal anglestherebetween. The vertices of the angles may be sharp and/or rounded. Inother embodiments, the curved facing surfaces may only include smoothlycurved portions without any sharp angles.

Specifically, referring to FIG. 11, a metal anode contact pad 220 and ametal cathode contact pad 230 are shown. As shown in FIG. 11, thecontact pads 220 and 230 are in the form of interlocking fingers, whichcan increase the stability and die attach area for lead frame packagesutilizing direct attach LED dies. Specifically, the metal anode pad 220includes a metal finger 220 f that extends toward the metal cathode pad230, and the metal cathode pad 230 includes a metal finger 230 f thatextends towards the metal anode pad 220.

Thus, as shown in FIG. 11, the gap G is not linear, but is curved andincludes three separate orthogonal line segments. Thus, the total lengthL of the gap G is longer than that of a straight line gap. The longerlength L between the adjacent of the adjacent ends 220 a and 230 a ofthe metal anode pad 220 and the metal cathode pad 230, respectively, andthe larger amount of plastic cup material in the elongated gap, canincrease the stability of the lead frame package, so that the metalanode contact 220 and the metal cathode contact 230 are more planar.Stated differently, curved facing surfaces 220 a, 230 a of the metalanode and cathode pads 220, 230 can increase the stability of the leadframe and/or the planarity of the anode and cathode pads 220, 230,respectively.

FIG. 12 illustrates an LED component that is fabricated from the leadframe of FIG. 11, wherein a single LED die 100 is mounted on the leadframe having the curved facing surfaces. As shown, the LED die 100 isdisposed in the cup 240 such that the outer face of the anode contact(not illustrated for clarity) is closely spaced apart from the metalanode pad 220 adjacent a first one of the line segments (the middle orhorizontal facing surface 220 a) and the outer face of the cathodecontact (not illustrated for clarity) is closely spaced apart from themetal cathode pad 230 adjacent the first one of the line segments 230 a(the middle or horizontal facing surface 230 a). The anode and cathodecontacts of the LED die may be sized and shaped appropriately to attachto the curved mating surfaces. In some embodiments, the anode andcathode contacts of the LED die may also have curved facing surfacestherebetween that correspond to the curved facing surfaces in the leadframe, so that a single LED die can span multiple line segments. FIG. 12may also be regarded as illustrating an LED component wherein one of themetal anode pad or the metal cathode pad includes three edges, and theother of the metal cathode pad or the metal anode pad extends adjacentthe three edges.

FIG. 13A illustrates multi-die embodiments of FIG. 12, wherein multipleLED dies 100 are used, a respective one of which spans a respective linesegment in the curved facing surfaces. In embodiments of FIG. 13A, as inFIG. 12, the curved facing surfaces can provide increased stability tothe package. Moreover, the per-segment arrangement of LED dies may allowspacing of the LED dies 100 farther apart from one another than may bethe case for multiple LED dies spanning straight facing surfaces. Theconfigurations may be symmetric, as illustrated in FIG. 13A, or may beasymmetric, wherein different dies and/or die spacings are used and/orasymmetric curves or line segments are used.

FIG. 13B illustrates other embodiments wherein the metal anode pad 220and the metal cathode pad 230 both include five facing line segments 220a, 230 a. Again, a respective LED die spans a respective line segment inthe curved facing surfaces.

In all of the embodiments illustrated above, a single metal anode pad220 and a single metal cathode pad 230 are provided in each LEDcomponent. In other embodiments, multiple metal anode pads and/ormultiple metal cathode pads may be provided. For example, FIG. 14illustrates additional embodiments of interlocking lead frame pads. Inthese embodiments, a single metal anode pad 220 and two metal cathodepads 230′ and 230″ are provided. The tabs 1410 on the metal anode pad220 are provided so that the metal anode pad 220 may be attached toother elements of the lead frame during fabrication. In otherembodiments, however, the tabs 1410 are not needed, and the metal anodepad 220 may be completely surrounded by the gap G, to provide a floatingisland metal anode pad. The central metal anode pad 220 is stabilized bythe large amount of overlap among the facing surfaces 220 a, 230 a,which provide an extended length of the cup material in the gap G.

FIG. 15 illustrates the lead frame of FIG. 14 with four LED dies 100thereon. This component can provide two parallel strings of two LED dieseach. Various other configurations also may be provided. They can besymmetric or asymmetric with respect to the dies and/or pads. It will beunderstood that various configurations of LED wiring may be provided byembodiments of FIGS. 14 and 15, depending upon the placement of theanode and cathode contacts of the LED dies 100 on the lead frame ofFIGS. 14 and 15. For example, in some embodiments of FIG. 15, the anodecontact of the four LED dies 100 may be die attached to the metal anodepad 220, the cathodes of two of these LED dies may be die attached tothe first metal cathode pad 230′ and the cathode contacts of theremaining two LED dies may be die attached to the second metal cathodepad 230′. In other embodiments, the anode contacts of two of the LEDdies and the cathode contacts of the remaining two LED dies are dieattached to the pad 220, the anode contacts of the first two LED diesare die attached to the pad 230′ and the cathode contacts of theremaining two LED dies are die attached to the pad 230″ of FIG. 15, toprovide two anti-parallel strings of two LED dies each. In theseembodiments, the three metal pads 220, 230′ and 230″ may not provide ananode or a cathode for the component, but still may provide externalconnections for the component. Accordingly, depending upon the wiring ofthe LEDs, the terms “anode” and “cathode” may not apply to the pads 220,230′ and 230″.

FIG. 16 illustrates another lead frame arrangement wherein only a singletab 1410 is provided to support the metal anode pad 220, and a singlemetal cathode pad 230 almost completely surrounds the metal anode pad onfour sides thereof. FIG. 17A illustrates an LED component using the leadframe of FIG. 16 including four LED dies 100 thereon that areelectrically connected in parallel. Accordingly, FIG. 17A illustratesvarious embodiments wherein one of the metal anode pad or the metalcathode pad includes four edges, and the other of the metal cathode pador the metal anode pad extends adjacent the four edges. It will beunderstood that more than four edges also may be included in otherembodiments. Thus, the metal anode pad and/or metal cathode pad may bepentagonal, hexagonal, octagonal, etc. It will also be understood thatmore or fewer LED dies may be included in an LED component and may beconnected in series and/or in parallel. The LED dies 100 need not be thesame as one another nor need they be placed symmetrically. For example,one or more of the LED dies 100 may be a blue shifted yellow LED die,whereas one or more of the LED dies may be a red LED die. FIG. 17Billustrates another configuration. Instead of a tab 1410, the anodecontact pad 220 is extended compared to FIG. 17A.

FIG. 17C illustrates other embodiments wherein the metal anode pad 220and the metal cathode pad 230 each includes five facing line segments220 a, 230 a, and wherein five LEDs 100 are used, a respective one ofwhich is on a respective pair of facing line segments.

In conclusion, FIGS. 5-17 illustrated various embodiments where themetal anode pad 220, the metal cathode pad 230 and/or the plastic cup240 are configured to facilitate the direct electrical connection of theouter face 160 o of the anode contact 160 to the exposed portion 220 eof the metal anode pad 220, and the direct electrical connection of theouter face 170 o of the cathode contact 170 to the exposed portion 230 eof the metal cathode pad 230, by the die attach layer 180′. Althoughvarious embodiments described above have been presented independently by(a) increasing the extension of the cup base relative to the gap; (b)providing temporary links; and (c) providing curved facing surfaces;these embodiments may also be provided in various combinations orsubcombinations. For example, the increased distance (a) may be combinedwith temporary links (b) and/or may be combined with curved facingsurfaces (c). Alternatively, the temporary links (b) may be combinedwith the increased extension (a) and/or the curved surfaces (c).Moreover, the curved surfaces (c) may be combined with the increasedextension (a) and/or the temporary links (b). Finally, the increasedextension (a), the temporary links (b) and the curved facing surfaces(c) may all be provided in an LED component. Any of these combinationscan thereby facilitate the direct attachment of an LED die to a leadframe.

Die Attach Layer Configuration

Various embodiments that now will be described configure the die attachlayer itself to facilitate the direct electrical connection of the outerface of the anode contact to the exposed portion of the metal anode padand the direct electrical connection of the outer face of the cathodecontact to the exposed portion of the metal cathode pad, by the dieattach layer. In the embodiments that will now be described, the dieattach layer may be configured by (a) configuring the thickness thereofand/or by (b) configuring the composition thereof. Either or both ofthese configurations can facilitate the direct die attach of an LED dieto a lead frame. Moreover, either or both of these configurations may becombined with any combination of one or more of the three configurationsthat were described above in connection with the metal pads and/orplastic cup.

(a) Configuring the Thickness of the Die Attach Layer

As was described above, due to the flexibility of the lead framepackage, the metal anode pad 220 and the metal cathode pad 230 deviatefrom coplanarity. Thus, as shown in FIG. 18, there may be a heightdifference H between the adjacent ends 220 a, 230 a, respectively,thereof. Conventionally, die attach layers having a thickness of 3 μm orless are generally used for die attaching an LED die to a ceramic orother nonflexible substrate.

Various embodiments that now will be described may arise fromrecognition that a conventional die attach thickness may not besufficient to allow an LED die to be die attached across these unevensurfaces with high component yield. In sharp contrast, variousembodiments described herein and as illustrated in FIG. 18, provide adie attach layer 180′ that is thicker than the height difference Hbetween the metal anode pad 220 and the metal cathode pad 230.Specifically, referring to FIG. 18, the exposed portions 220 e and 230 eof the metal anode pad 220 and the method cathode pad 230, respectively,deviate from coplanarity by a height difference H. In some embodiments,H is measured at the adjacent ends 220 a, 230 a of the metal anode padand metal cathode pad 220, 230, respectively. In other embodiments, thedeviation from planarity H may be measured at other places on the metalpads.

As illustrated in FIG. 18, the die attach layer 180′ has a thickness Tthat is thicker than the height difference H. Thus, T>H. In otherembodiments, as illustrated in FIG. 19, T is also thicker than 3 μm.Thus, in FIG. 19, the die attach layer 180′ has a thickness T greaterthan the height difference H that was illustrated in FIG. 18 and that isalso greater than 3 μm.

In a specific example, it may be difficult to bond an LED die 100 havinga 3 μm die attach layer 180 thereon, across two floating metal pads 220,230 having a 4 μm height difference H, with high process yield. The LEDdie may be tilted and/or the die attach may fail during subsequentfabrication or use. In sharp contrast, when the thickness T of the dieattach layer 180′ is increased to be greater than the height differenceH, high process yields may be provided during die attach. Otherexperiments have found a 5 μm height difference between the two pads, sothat a die attach thickness of at least 5 μm may be used.

FIG. 20 illustrates a conventional LED die that is used for die attachto a ceramic or other nonflexible submount. As shown in FIG. 20, thethickness T of the conventional die attach layer 180 is less than 3 μm.

FIG. 21 illustrates other embodiments wherein the die attach layer 180′is of different thickness on the outer face 160 o of the anode contact160 compared to on the outer face 170 o of the cathode contact 170.Embodiments of FIG. 21 may arise from recognition that in some leadframes, the height difference H that was illustrated in FIG. 18 is oftenconsistent from component to component. For example, as was illustratedin FIG. 18, the smaller metal anode pad 220 may consistently curveupward relative to the larger metal cathode pad 230. If this is thecase, the thickness of the die attach layer 180′ on the anode contact160 may be made different than the thickness of the die attach layer180′ on the cathode contact 170. Thus, as illustrated in FIG. 21, in theconfiguration of FIG. 18, where the metal anode pad 220 is higher thanthe metal cathode pad 230, the die attach layer 180′ on the cathodecontact 170 may have a thickness T2 that is greater than the thicknessT1 of the die attach layer 180′ on the anode contact 160. Stateddifferently, T2>T1. Moreover, in some embodiments, the differencesbetween the thicknesses may correspond to the height difference H, i.e.,T2−T1=H. In yet other embodiments, T1 may also be at least 3 μm thick.

Accordingly, embodiments of FIGS. 18-19 and 21 can at least partiallycompensate for the height difference H between adjacent ends 220 a, 220b of the lead frame metal anode and cathode pads 220, 230, respectively,by providing a die attach layer that is at least as thick as this heightdifference H. The die attach layer 180′ may include ratios of AuSn(gold-tin), NiSn (nickel-tin) and/or other eutectic or non-eutecticmixtures of Au, Ni, Sn, Sb, As, Ta, Co, Mn and/or other 3d, 4d, 5d, or fblock transition metals. Moreover, the thickness of the die attachmaterial need not be uniform across the LED die. The die attachthickness may also be different as between the anode and cathode, toaccommodate different relative heights of the bonding locations on thelead frame. Thus, thicker and/or asymmetric die attach layers may beprovided.

(b) Die Attach Composition

Various embodiments described above varied the thickness of the dieattach layer, but may use a conventional binary die attach layer.Various embodiments that will now be described use a ternary soldercomprising Gold (Au), Nickel (Ni) and Tin (Sn). This ternary die attachcomposition may be used separately, may be used with the die attachthickness described above and/or may be used with any or all of theconfigurations of the metal anode pad, metal cathode pad and/or theplastic cup that were described above. It will be understood that theterm “ternary” also includes quaternary and higher order combinations ofmetals in the die attach layer. Eutectic or non-eutectic combinationsmay be provided.

Various weight percent (wt %) ranges of the Au, Ni and Sn may beprovided according to various embodiments described herein, as isillustrated in the following Table:

TABLE Ranges of Solder Compositions (wt %) Au Ni Sn  0 < Au ≦ 10 10 ≦ Ni≦ 60 40 ≦ Sn ≦ 90 0.8 ≦ Au ≦ 4.5 19 ≦ Ni ≦ 41 55 ≦ Sn ≦ 80Note in the above Table, all of the ranges are expressed in weightpercent (wt %) and, in a specific composition of the solder, all of thewt % s need to add up to 100 wt % (unless other materials are alsoincluded).

Ternary solder compositions according to various embodiments describedherein may have at least two desirable properties to facilitate directdie attach to lead frames. These two properties relate to low meltingtemperature and different melting and re-melting temperatures.

As to melting temperature, the ternary die attach materials described inthe above Table have an initial melting temperature of between 250° C.and 260° C. In sharp contrast, Au—Sn solders that are conventionallyused in the LED industry have a melting point of 282° C. This meltingtemperature of 250° C.-260° C. is less than the decompositiontemperature of silicone (for example, 350° C.).

Moreover, ternary solder compositions according to various embodimentsdescribed herein have a re-melting temperature that is higher than theinitial melting temperature (also simply referred to as the “meltingtemperature”). Specifically, the ternary solder compositions may notre-melt until at least 400° C., and in some embodiments at 485° C. Insharp contrast, conventional Au—Sn solders will re-melt again at theirmelting point of 282° C. after cycling.

Thus, solder compositions according to various embodiments describedherein can provide an initial melt interval at a low temperature, butcan form phases of a significantly higher temperature uponsolidification that enables them to survive (i.e., not re-melt during)typical lead-free reflow processes that are used to attach an LEDcomponent to a board. Accordingly, ternary solders according to variousembodiments described herein can achieve low melting temperatures (below260° C.), which allows die attachment in lead frames that are prone tomelting, such as silicone lead frames. Moreover, the composition willnot re-melt when re-exposed to typical lead-free reflow profiles, whichcan ensure the integrity of the electrical and thermal contacts.Accordingly, the die attach material will not re-melt when subject toattaching the finished component to a board. Re-melting at this pointmay compromise the bond integrity and can lead to failure.

FIG. 22 is a phase diagram illustrating properties of ternary Au Ni Snsolder compositions according to various embodiments described hereinduring melting and re-melting. As shown in FIG. 22, initial meltingtakes place between 250° C. and 260° C. However, subsequent re-meltingtakes place at temperatures greater than 400° C.

Having been made aware of the desirable characteristics of the dieattach material described above, those skilled in the art may envisionquaternary modifications and/or additional ternary solders that may alsoprovide these characteristics.

Fabrication

FIG. 23 is a flowchart of operations that may be performed to fabricateLED components according to various embodiments described herein.Referring to FIG. 23, at Block 2310, a lead frame structure is provided.A lead frame structure that may be used according to various embodimentsdescribed herein is illustrated in FIG. 24. An individual lead framecomprises a metal anode pad, a method cathode pad and a plastic cup onthe metal anode pad and the metal cathode pad that defines an exposedportion of the metal anode pad and an exposed portion of the metalcathode pad. The metal anode pad, the metal cathode pad and/or theplastic cup may be configured according to any of the embodimentsdescribed above. The lead frame structure may be provided as an array ofindividual lead frames, so that multiple components may be fabricatedtogether.

At Block 2320, LED dies are provided. As was described above, each LEDdie comprises first and second opposing faces, an anode contact and acathode contact on the first face thereof, and a die attach layer on theouter faces of the anode and cathode contacts remote from the LED die.The die attach layer may be configured to according to any of theembodiments described above.

It will be understood that operations of Block 2310 may be performed bya lead frame fabricator and operations at Block 2320 may be provided byan LED die manufacturer. These manufacturers may be same or differententities using the same or different fabrication facilities. Generally,LED die manufacture is more high-tech than lead frame manufacture.

At Block 2330, die attach is performed. Specifically, as was describedabove, the LED die is placed in the cup, such that the die attach layeris directly on the exposed portion of the metal anode and the exposedportion of the metal cathode pad. The die attach layer is then melted sothat the die attach layer directly electrically connects the outer faceof the anode contact to the exposed portion of the metal anode pad anddirectly electrically connects the outer face of the cathode contact tothe exposed portion of the metal cathode pad. Encapsulation may beperformed at Block 2340. The LED components are then singulated at Block2350, for example using punching along the lines 2410 of FIG. 24. Thesingulated LED components are then mounted on a board at Block 2360.

CONCLUSION

Various embodiments described herein can directly die attach an LED dieto a lead frame by configuring a metal anode pad, a metal cathode pad, aplastic cup and/or a die attach material, according to variousembodiments described herein. These embodiments may be used in variouscombinations and subcombinations allow low cost lead frames to be usedwith direct attach LED dies.

Various embodiments described herein may also include a layer comprisingluminophoric material, also referred to as a phosphor layer. In someembodiments, the phosphor layer is a conformal phosphor layer that maybe less than 150 μm thick in some embodiments, less than 100 μm thick inother embodiments and less than 50 μm thick in yet other embodiments. Itwill be understood that the term “phosphor” is used herein to denote anywavelength conversion material, and may be provided according to variousconfigurations. The phosphor layer may also be any type of functionallayer or layers, such as any layer disposed to affect the properties ofthe emitted light, for example, color, intensity and/or direction.

Various techniques may be used to apply the phosphor layer, includingdispensing, screen printing, film transfer, spraying, coating and/orother techniques. Phosphor preforms also may be applied. In someembodiments, the phosphor layer may comprise silicone and/or othertransparent material having phosphor particles therein. It will also beunderstood that the phosphor layer may be coplanar with the outer faceof the LED dies. However, the outer or edge portions of the phosphorlayer need not be co-planar with these outer faces. Specifically, it canbe recessed from the outer faces or may protrude beyond the anode andcathode contacts.

The phosphor layer may be a thin conformal layer having uniform phosphorparticle density. However, a phosphor layer may be provided thatcomprises phosphor particles that are nonuniformly dispersed therein,and that, in some embodiments, may include a phosphor-free region at theexterior surfaces of the phosphor layer. Moreover, the phosphor layermay also be configured as a conformal layer.

The phosphor layer, or any wavelength conversion layer, converts aportion of the light emitted from the LED die to a different wavelength,a process that is known in the art. One example of this process, isconverting a portion of blue-emitted light from light emitter, such asan LED die, to yellow light. Yttrium aluminum garnet (YAG) is an exampleof a common phosphor that may be used.

In some embodiments, the phosphor particles comprise many differentcompositions and phosphor materials alone or in combination. In oneembodiment the single crystalline phosphor can comprise yttrium aluminumgarnet (YAG, with chemical formula Y₃Al₅O₁₂). The YAG host can becombined with other compounds to achieve the desired emissionwavelength. In one embodiment where the single crystalline phosphorabsorbs blue light and reemits yellow, the single crystalline phosphorcan comprise YAG:Ce. This embodiment is particularly applicable to lightemitters that emit a white light combination of blue and yellow light. Afull range of broad yellow spectral emission is possible usingconversion particles made of phosphors based on the(Gd,Y)₃(Al,Ga)₅O₁₂:Ce system, which include Y₃Al₅O₁₂:Ce (YAG). Otheryellow phosphors that can be used for white emitting LED chips include:

-   -   Tb_(3-x)Re_(x)O₁₂:Ce (TAG);    -   RE=Y, Gd, La, Lu; and/or    -   Sr_(2-x-y)Ba_(x)Ca_(y)SiO₄:Eu.

In other embodiments, other compounds can be used with a YAG host forabsorption and re-emission of different wavelengths of light. Forexample, a YAG:Nb single crystal phosphor can be provided to absorb bluelight and reemit red light. First and second phosphors can also becombined for higher CRI white (i.e., warm white) with the yellowphosphors above combined with red phosphors. Various red phosphors canbe used including:

-   -   Sr_(x)Ca_(1-x)S:Eu,Y; Y=halide;    -   CaSiAlN₃:Eu; or    -   Sr_(2-y)Ca_(y)SiO₄:Eu.

Other phosphors can be used to create saturated color emission byconverting all light to a particular color. For example, the followingphosphors can be used to generate great saturated light:

-   -   SrGa₂S₄:Eu;    -   Sr_(2-y)Ba_(y)SiO₄:Eu; or    -   SrSi₂O₂N₂:Eu.

The following lists some additional suitable phosphors that can be usedas conversion particles, although others can be used. Each exhibitsexcitation in the blue and/or UV emission spectrum, provides a desirablepeak emission, has efficient light conversion:

Yellow/Green

-   -   (Sr,Ca,Ba)(Al,Ga)₂S₄:Eu²⁺    -   Ba₂(Mg,Zn)Si₂O₇Eu²⁺    -   Gd_(0.46)Sr_(0.31)Al_(1.23)O_(x)F_(1.38): Eu²⁺ _(0.6)    -   (Ba_(1-x-y)Sr_(x)Ca_(y))SiO₄:Eu    -   Ba₂SiO₄=Eu²⁺

Red

-   -   Lu₂O₃=Eu³⁺    -   (Sr_(2-x)La_(x))(Cei_ _(x) Eu_(x))O₄    -   Sr₂C_(1-x)Eu_(x)O₄    -   SrTiO₃:Pr³⁺, GA³⁺    -   CaAlSiN₃IEu²⁺    -   Sr₂Si₅N₈=Eu²⁺

In some embodiments, the layer comprising luminophoric material and/orthe encapsulant may also provide a functional layer which comprises alight scattering layer, which comprises a binder material as discussedabove and light scattering particles, for example titanium oxideparticles. In other embodiments, the layer comprises materials to alterthe refractive index of the functional layer. In some embodiments, thefunctional layer comprises a combination of one or more of the types offunctional layers described herein (e.g. a wavelength conversion layerand a scattering or refractive index altering layer).

In some embodiments, the LED die is configured to emit blue light, forexample light having a dominant wavelength of 450-460 nm, and thephosphor layer comprises yellow phosphor, such as YAG:Ce phosphor,having a peak wavelength of 550 nm. In other embodiments, the LED die isconfigured to emit blue light upon energization thereof, and thephosphor layer may comprise a mixture of yellow phosphor and redphosphor, such CASN-based phosphor. In still other embodiments, the LEDdie is configured to emit blue light upon energization thereof, and thephosphor layer may comprise a mixture of yellow phosphor, red phosphorand green phosphor, such as LuAG:Ce phosphor particles. Moreover,various combinations and subcombinations of these and/or other colorsand/or types of phosphors may be used in mixtures and/or in separatelayers. In still other embodiments, a phosphor layer is not used. Forexample, a blue, green, amber, red, etc., LED need not use phosphor. Inembodiments which do use a phosphor, it may be beneficial to provide auniform coating in order to provide more uniform emissions.

The encapsulant, which may also be referred to herein as “opticalcoupling material”, may comprise silicone without phosphor particlestherein, and may provide a primary optic for the light emitting device.The optical coupling material that is free of phosphor may be shaped toprovide a lens, dome and/or other optical component, so that the sidesand/or tops thereof may be oblique to the diode region. The opticalcoupling material that is free of phosphor may also encapsulate thephosphor layer and/or light emitting surfaces of the LED die. Theoptical coupling layer may be at least 1.5 mm thick in some embodiments,at least 0.5 mm thick in other embodiments, and at least 0.01 mm thickin yet other embodiments, and may not be present in still otherembodiments. Thus, in other embodiments, an optical coupling materiallayer may be used without a phosphor layer. For example, the opticalcoupling material may be directly on the second face of the LED die. Insome embodiments, a relatively thick transparent layer may be used. Inother embodiments, a conformal transparent layer may be used. In stillother embodiments, the transparent layer may be provided on a phosphorlayer that comprises phosphor particles that are non-uniformly dispersedtherein. The device may further include an additional encapsulant orlens, which may be silicone or glass. Other embodiments may not includethis additional lens.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, the present specification, including the drawings, shall beconstrued to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A Light Emitting Diode (LED) component comprising: a lead frame thatcomprises a metal anode pad, a metal cathode pad and a plastic cup onthe metal anode pad and the metal cathode pad that defines an exposedportion of the metal anode pad and an exposed portion of the metalcathode pad in the plastic cup; an LED die that comprises first andsecond opposing faces and an anode contact and a cathode contact on thefirst face thereof, the anode and cathode contacts including outer facesremote from the LED die, the LED die being disposed in the plastic cupsuch that the outer face of the anode contact is closely spaced apartfrom the exposed portion of the metal anode pad and the outer face ofthe cathode contact is closely spaced apart from the exposed portion ofthe metal cathode pad; and a die attach layer that extends between theouter face of the anode contact and the exposed portion of the metalanode pad and between the outer face of the cathode contact and theexposed portion of the metal cathode pad and that directly electricallyconnects the outer face of the anode contact to the exposed portion ofthe metal anode pad and directly electrically connects the outer face ofthe cathode contact to the exposed portion of the metal cathode pad. 2.The LED component according to claim 1 wherein the exposed portions ofthe metal anode and cathode pads are not coplanar.
 3. The LED componentaccording to claim 1 wherein the plastic cup comprises silicone.
 4. TheLED component according to claim 1 wherein the metal anode pad, themetal cathode pad and/or the plastic cup are configured to facilitatethe direct electrical connection of the outer face of the anode contactto the exposed portion of the metal anode pad and the direct electricalconnection of the outer face of the cathode contact to the exposedportion of the metal cathode pad, by the die attach layer.
 5. The LEDcomponent according to claim 4 wherein adjacent ends of the metal anodepad and the metal cathode pad define a gap therebetween, wherein theplastic cup extends in the gap and also extends beyond non-adjacent endsof the metal anode pad and the metal cathode pad by a distance, andwherein the distance is larger than the gap.
 6. The LED componentaccording to claim 5 wherein the distance is at least 10% larger thanthe gap.
 7. The LED component according to claim 4 wherein adjacent endsof the metal anode pad and the metal cathode pad have different widths.8. The LED component according to claim 4 wherein the plastic cupextends on opposite faces of the metal anode pad and/or the metalcathode pad.
 9. The LED component according to claim 4 wherein the leadframe further comprises a metal link that mechanically connects themetal anode pad to the metal cathode pad outside the plastic cup. 10.The LED component according to claim 9 wherein the metal link isconfigured to be sheared from the metal anode pad and/or the metalcathode pad.
 11. The LED component according to claim 9 wherein themetal link comprises a fusible metal.
 12. The LED component according toclaim 4 wherein adjacent ends of the metal anode pad and the metalcathode pad include curved facing surfaces.
 13. The LED componentaccording to claim 12 wherein the curved facing surfaces comprise aplurality of line segments that form oblique and/or orthogonal anglestherebetween.
 14. The LED component according to claim 13 wherein theLED die is a first LED die disposed in the plastic cup such that theouter face of the anode contact is closely spaced apart from the metalanode pad adjacent a first one of the line segments and the outer faceof the cathode contact is closely spaced apart from the metal cathodepad adjacent the first one of the line segments; the LED componentfurther comprising a second LED die that also comprises first and secondopposing faces and an anode contact and a cathode contact on the firstface thereof, the anode and cathode contacts including outer facesremote from the second LED die, the second LED die being disposed in theplastic cup such that the outer face of the anode contact is closelyspaced apart from the metal anode pad adjacent a second one of the linesegments and the outer face of the cathode contact is closely spacedapart from the metal cathode pad adjacent the second one of the linesegments.
 15. The LED component according to claim 4 wherein the metalanode pad includes a metal finger that extends toward the metal cathodepad and wherein the metal cathode pad includes a metal finger thatextends toward the metal anode pad.
 16. The LED component according toclaim 4 wherein one of the metal anode pad or the metal cathode padincludes three edges and the other of the metal cathode pad or the metalanode pad extends adjacent the three edges.
 17. The LED componentaccording to claim 4 wherein one of the metal anode pad or the metalcathode pad includes four edges and the other of the metal cathode pador the metal anode pad extends adjacent the four edges.
 18. The LEDcomponent according to claim 1 wherein the die attach layer isconfigured to facilitate the direct electrical connection of the outerface of the anode contact to the exposed portion of the metal anode padand the direct electrical connection of the outer face of the cathodecontact to the exposed portion of the metal cathode pad, by the dieattach layer.
 19. The LED component according to claim 18: wherein theexposed portions of the metal anode and cathode pads deviate fromcoplanarity by a height difference, and wherein the die attach layer isthicker than the height difference.
 20. The LED component according toclaim 19 wherein the die attach layer is also thicker than 3 μm.
 21. TheLED component according to claim 18 wherein the die attach layer is ofdifferent thickness between the outer face of the anode contact that isclosely spaced apart from the exposed portion of the metal anode padcompared to between the outer face of the cathode contact that isclosely spaced apart from the exposed portion of the metal cathode pad.22. The LED component according to claim 18 wherein the die attach layercomprises a solder comprising Gold (Au), Nickel (Ni) and Tin (Sn). 23.The LED component according to claim 22 wherein 0<Au wt %≦10, 10≦Ni wt%≦60 and 40≦Sn wt %≦90.
 24. The LED component according to claim 23wherein 0.8≦Au wt %≦4.5, 19≦Ni wt %≦41 and 55≦Sn wt %≦80.
 25. The LEDcomponent according to claim 18 wherein the plastic cup comprisessilicone and wherein the die attach layer has a melting temperaturebelow a decomposition temperature of the silicone.
 26. The LED componentaccording to claim 18 wherein the die attach layer has a meltingtemperature below 260° C.
 27. The LED component according to claim 18wherein the die attach layer has a inciting temperature and has are-melting temperature that is higher than the inciting temperature. 28.The LED component according to claim 27 wherein the melting temperatureis below 260° C. and the re-melting temperature is above 260° C.
 29. ALight Emitting Diode (LED) component comprising: a lead frame; and anLED die that is electrically connected to the lead frame without wirebonds. 30.-33. (canceled)
 34. A lead frame comprising: a metal anode padand a metal cathode pad; a plastic cup on the metal anode pad and themetal cathode pad that defines an exposed portion of the metal anode padand an exposed portion of the metal cathode pad in the plastic cup; themetal anode pad, the metal cathode pad and/or the plastic cup beingconfigured to facilitate a direct solder connection of respective anodeand cathode contacts of a Light Emitting Diode (LED) die to therespective exposed portion of the metal anode pad and the exposedportion of the metal cathode pad. 35.-48. (canceled)
 49. A LightEmitting Diode (LED) comprising: an LED die that comprises first andsecond opposing faces and an anode contact and a cathode contact on thefirst face thereof, the anode and cathode contacts including outer facesremote from the LED die; and a die attach layer on the outer faces ofthe anode contact and the cathode contact that is configured tofacilitate a direct attachment of the die attach layer to metal anodeand cathode pads of a lead frame. 50.-60. (canceled)